I'm going to be disliked because of what I'm going to say, but because of the lack of interest in the 1v1/2v2 featured game mode that existed a while ago (Showdown), I feel they scrapped much of the intent in making such a map. I know a bunch of people that visit the forums probably played the game mode a lot during it's existence, but the small interest in the mode dropped off a bunch. Brackhar said that "[i]f the modes were left on permanently, the queue times for each would be pretty atrocious after a few more weeks." He also later brought up that there was always the case where the mode will come back in the future, but I don't think there will be any plans of keeping 1v1/2v2 or any of the other featured game modes available for a longer duration than a couple weeks at most. Long story short, enjoy the mode when/if it comes back. =]
Thread I reference Brackhar from: http://forums.na.leagueoflegends.com/board/showthread.php?t=4186837